One day, 6-year-old Keira Vidikan developed a minor headache just before heading off to her ballet class in Dayton, Ohio. Less than two weeks later, she was in a coma at the Cleveland Clinic, nearly paralyzed and unable to speak.

"I think this was the darkest night we will ever have," said her mother, Michelle Vidikan.

After scanning Keira's brain, emergency room doctors suspected a glioma, an aggressive form of brain cancer. As Vidikan and her husband, Mario, waited out the night at the local hospital, their daughter was slowly dying.

But in the morning, after six hours of tests, there was a ray of hope. An MRI showed the mass was more vascular in nature, and Keira was referred to the Cleveland Clinic for an evaluation.

Keira was diagnosed with cavernoma, a rare form of a family of conditions known as arteriovenous malformations or AVMs. A cluster of extra blood vessels had formed on her brain stem and had hemorrhaged. It was not cancer.

In December, Keira was a breath away from death, but today, she has returned to school thanks to prompt attention from her parents, both optometrists, and surgeons at Cleveland Clinic.

"She is back to running, dancing, jumping, and skipped her way out of the clinic today," Vidikan told ABCNews.com today after Keira's latest follow-up visit.

About 300,000 Americans suffer from AVMs, which are defects of the circulatory system that are generally believed to arise during embryonic or fetal development or soon after birth, according to the Cleveland Clinic. Although they can develop anywhere in the body, those in the brain or spinal cord can have devastating effects on the body.

"No one really understands these cavernomas very well," he said. "A lot of them grow and stabilize at a small size. She also had an unusual subset that was progressively enlarging over time. She was four or five weeks into this, and hers was just growing and growing like an aggressive tumor."

Keira's condition only occurs at a rate of about 1 in 500,000 in the general population, according to Rasmussen.

"It's a lot more common in women in their early 40s," Rasmussen said. "It's relatively rare in children."

Usually, the patient is treated with steroids and observation, but Keira was "clearly deteriorating," he said.

The greatest danger, as in Keira's case, is bleeding, which happens only in about 2 to 4 percent of all AVMs. Without prompt treatment, she could have also suffered a stroke, according to Rasmussen.

Surgery is the only treatment, but that, too, can be risky.

"The brain stem sits right smack dab in the middle of your head, and you've got to get into that area," he said. "The brain stem is sort of like an octopus with arms and nerves that provide movement to the face, eyes, mouth and lips, so you have to be able to work in between the nerves to get in to the substance of the brain itself and move it and pull it out of there.

"She's absolutely a real fire plug and the clearly the darling of her parents," said Rasmussen, who was happily surprised with Keira's quick bounce-back. "She's an absolute gem."

Keira had been a healthy child, so when she first started complaining about a headache, her parents thought it was just nerves.

"She had never complained about one before and we blew it off," said her mother. "But the next day, she came home from school and complained about the same thing."

As optometrists, the Vidikans often see children complain of headaches because of vision problems.

"They are usually not severe, and you continue to monitor and give them an eye exam," she said.

But just a few days later, the family was sitting around the kitchen counter when, all of a sudden, Keira fell off a bar stool. Still, she otherwise seemed fine.

"She took a bath and did her homework," said Vidikan. "But the next day, Dec. 7, everything went wrong. In the morning we went to school and she had a hard time putting her right arm through the jacket of her coat sleeve."

Later, she "stumbled out" of the van when they arrived at school. At dinner that night, Keira was not using her right arm to eat. They also noticed she had begun to limp.

"We started to get concerned," said Vidikan. "Maybe she hurt herself in the fall."

But the next morning, Keira was slurring her words. Her parents were now alarmed that something more serious was going on.

"We just knew," said her mother.

Once Near Death, Ohio Girl Is Now Back at School

The Vidikans took Keira to the local emergency room for an x-ray. Everything looked normal, so the ER doctor told the family to go home.

"But within five minutes, he came back into our room and drew the curtain and turned off the TV," said Vidikan, fighting back tears. "The radiologist found a problem in the brain stem."

But doctors could do nothing until the bleeding stopped and so they sent Keira home.

"That weekend she got worse," said her mother. "She was very, very drowsy and lethargic, and her strength was going."

When Keira arrived at the Cleveland Clinic on Monday, she had near-complete paralysis on the right side of her body, including her face, and her speech was slurred.

"The most noticeable thing was she was becoming very lethargic," said Rasmussen. "The brain stem area of the brain coordinates wakefulness. She had such pressure and distortion of the brain stem that she was heading toward coma. If this had gone on for a few more weeks, she would have died."

Vidikan said Rasmussen was "very plainspoken and confident, as well."

She knew surgery, which was scheduled for Dec. 20, would be risky.

The results were a "miracle," said Vidikan. Keira was discharged from the hospital on Christmas Eve.

"It was a great Christmas present for everyone," said Rasmussen.

Brain images show complete removal of the lesion.

"She should be cured and neurologically recovered almost completely," Rasmussen said. "The last time I saw her she was dragging her right foot, but it wasn't even noticeable two weeks after surgery."

That, according to her mother after the latest visit, has disappeared.

"Literally within hours, she was regaining neurological function," she said. "It's amazing how quickly it was. We thought she would always have a limp and slow speech, and maybe not have use of her arm again. But Christmas Eve, hour by hour, she was moving her fingertips and moving her arm.

"My husband and I talk about the irony of it," said Vidikan. "We met in optometry school and in neuroanatomy lab evaluating brain slices. I never dreamt that 13 years later it would come to any use."